This invention relates to compositions which are used to produce high-strength ceramic/polymer composite shaped articles and to methods of producing shaped articles from those compositions.
Prior workers have devised procedures for making shaped articles from ceramic and polymer powders. For instance, clay compositions have been mixed with thermosetting resins such as phenolic and thermoplastic resins such as polyethylene and formed into shapes by conventional ceramic forming techniques such as slip casting and throwing on a potter's wheel. However, the strength properties of these articles have left much to be desired.
The present invention relates to a composition comprising about 15 to 35 wt.% (25 to 55 vol.%) aqueous phase and 65 to 85 wt.% (45 to 75 vol.%) solids, wherein the solids comprise about 5 to 25 wt.% (10 to 42 vol.%) on solids basis of finely divided epoxy resin powder and about 75 to 95 wt.% (58 to 90 vol.%) of finely divided ceramic powder. Using standard ceramic formulation practices for the above composition range, shaped articles can be made from slip and modeling clay. In any of these processes, the water remaining after the forming operation is allowed to evaporate through drying and the articles are permanently hardened by firing at low temperatures, for example, 150.degree.-200.degree. C. High strength articles are obtained by all forming processes. Of particular importance is that the compositions of the present invention may be made into a slip or modeling clay and the working and forming characteristics are equivalent to polymer-free ceramic compositions which are fired at high temperatures to obtain high strengths. Nor are the compositions limited to the above forming processes. For example, extruded shapes can be formed by forcing material, which contains about 15% moisture, through a die.
J. D. Sullivan and C. R. Austin, U.S. Pat. No. 2,288,047, issued June 30, 1942, describes slip cast ceramic bodies containing a major portion of plastic clay and 1 to 20 weight percent of a thermoset or thermoplastic resin, preferably 5 to 20 weight percent. The patentees indicate that equal flexural strengths can be obtained by using either a thermoplastic or thermosetting resin.
D. W. Dill, U.S. Pat. No. 3,817,897, issued June 18, 1974, describes a moist modeling clay composition consisting of water and a mixture of 75% to 90% by weight, based on dry ingredients, of a pottery clay and from 10% to 25% by weight of a powdered polymer selected from a group of high and low density polyethylenes, polypropylene, and ethylene vinyl acetate copolymer.